Dielectric ceramic composition and ceramic capacitor

ABSTRACT

The ceramic capacitor in accordance with the present invention is fabricated by employing a dielectric ceramic composition in forming dielectric layers thereof, wherein the dielectric ceramic composition contains an oxide of Ba and Ti, an oxide of Re (Re used herein represents one or more rare-earth elements selected from Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Tb and Y), an oxide of Mg, one or more oxides selected from oxides of Mn, V and Cr, an oxide of Mo and/or W and SiO 2  or a glass component including SiO 2 , wherein the amount of the oxide of Ba and Ti is 100 mol % in terms of BaTiO 3 , the amount of the oxide of Re is 0.25 to 1.5 mol % in terms of Re 2 O 3 , the amount of the oxide of Mg is 0.2 to 1.5 mol % in terms of MgO and the amount of one or more oxides of Mn, V or Cr is 0.03 to 0.6 mol % in terms of Mn 2 O 3 , V 2 O 5 , Cr 2 O 3 , respectively, and the amount of the oxide of Mo and/or W is 0.025 to 0.25 mol % in terms of MoO 3  and WO 3 .

FIELD OF THE INVENTION

The present invention relates to a ceramic capacitor and ceramic compositions therefor; and, more particularly, to reduction resistive dielectric ceramic compositions suitable for use as a dielectric layer of a ceramic capacitor having internal electrodes made of a base metal such as Ni and a ceramic capacitor fabricated by employing such ceramic compositions as a dielectric layer thereof.

BACKGROUND OF THE INVENTION

Recently, a base metal, e.g., Ni, is widely used in forming internal electrodes of multilayer ceramic capacitors for the purpose of reducing manufacturing costs. In case the internal electrodes are composed of the base metal, it is required that chip-shaped laminated bodies including therein the internal electrodes be sintered in a reductive atmosphere in order to prevent an oxidization of the internal electrodes. Accordingly, a variety of reduction resistive dielectric ceramic compositions have been developed.

Recent trend towards ever more miniaturized and dense electric circuits intensifies a demand for a further scaled down multilayer ceramic capacitor with higher capacitance. Keeping up with such demand, there has been made an effort to fabricate thinner dielectric layers and to stack a greater number of the thus produced dielectric layers.

However, when the dielectric layers are thinned out, a voltage applied to a unit thickness intrinsically increases. Accordingly, the operating life of the dielectric layers is shortened and thus a reliability of the multilayer ceramic capacitor is also deteriorated.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide highly reliable dielectric ceramic compositions and ceramic capacitors prepared by employing such dielectric ceramic compositions in forming dielectric layers thereof, wherein the dielectric ceramic compositions exhibit such electrical characteristics as a dielectric constant equal to or greater than 3000, a capacitance variation of −15% to +15% (based on a capacitance obtained at a temperature of +25° C.) in the temperature range from −55° C. to +125° C., a dielectric loss “tanδ” of 3.5% or less and an accelerated life of 200,000 seconds or greater.

In accordance with of the present invention, there is provided a dielectric ceramic composition comprising: 100 mol % of an oxide of Ba and Ti; 0.25 to 1.5 mol % of an oxide of Re, Re representing one or more elements selected from the group consisting of Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Y; 0.2 to 1.5 mol % of an oxide of Mg; 0.03 to 0.6 mol % of oxides of one or more elements selected from the group consisting of Mn, V and Cr; 0.025 to 0.25 mol % of oxides of one or two elements of Mo and W; and a glass component including SiO₂.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention will become apparent from the following description of a preferred embodiment given in conjunction with the accompanying drawings, in which:

FIG. 1 represents a schematic cross sectional view illustrating a multilayer ceramic capacitor;

FIG. 2 is a triangular composition diagram for showing compositions of B₂O₃—SiO₂-MO in a unit of mol %; and

FIG. 3 sets forth a triangular composition diagram for illustrating compositions of LiO₂—SiO₂-MO in a unit of mol %.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Compound powders of BaCO₃, TiO₂, Re₂O₃, MgO, Mn₂O₃, V₂O₅, Cr₂O₃, Fe₂O₃, NiO, CuO, MoO₃, WO₃ and a glass component including SiO₂ were weighed in amounts as specified in the accompanying Tables 1-1 and 1-6 and mixed for about 20 hours by a wet method in a ball mill containing therein PSZ (partially sterilized zirconia) balls and water to thereby obtain a ceramic slurry. The produced ceramic slurry was dehydrated and then dried by being heated at about 200° C. for 5 hours.

TABLE 1-1 Rare-earth Sample (Re₂O₃) Total Number Element Content MgO Mn₂O₃ V₂O₅ Cr₂O₃ Content MoO₃ Li₂O—  1 Ho 1.0 0.6 0.02 — — 0.02 0.1 0.1  2 Ho 1.0 0.6 —  0.02 — 0.02 0.1 0.1  3 Ho 1.0 0.6 — —  0.02 0.02 0.1 0.1  4 Ho 1.0 0.6 0.03 — — 0.03 0.1 0.1  5 Ho 1.0 0.6 — 0.03 — 0.03 0.1 0.1  6 Ho 1.0 0.6 — — 0.03 0.03 0.1 0.1  7 Ho 1.0 0.6 0.01 0.02 — 0.03 0.1 0.1  8 Ho 1.0 0.6 0.05 0.02 — 0.07 0.1 0.1  9 Ho 1.0 0.6 0.05 — 0.1 0.15 0.1 0.1 10 Ho 1.0 0.6 0.05 0.01 0.1 0.16 0.1 0.1 11 Ho 1.0 0.6 0.1 0.05 0.1 0.25 0.1 0.1 12 Ho 1.0 0.6 0.1 0.1 0.1 0.3 0.1 0.1 13 Ho 1.0 0.6 0.3 — — 0.3 0.1 0.1 14 Ho 1.0 0.6 — — 0.3 0.3 0.1 0.1 15 Ho 1.0 0.6 — — 0.3 0.3 0.1 0.1 16 Ho 1.0 0.6 0.6 — — 0.6 0.1 0.1 17 Ho 1.0 0.6 — — 0.6 0.6 0.1 0.1 18 Ho 1.0 0.6 — — 0.6 0.6 0.1 0.1 19 Ho 1.0 0.6 0.3 0.3 — 0.6 0.1 0.1 20 Ho 1.0 0.6 0.3 — 0.3 0.6 0.1 0.1 21 Ho 1.0 0.6 — 0.3 0.3 0.6 0.1 0.1 22 Ho 1.0 0.6 0.2 — 0.4 0.6 0.1 0.1 23 Ho 1.0 0.6 0.1 — 0.5 0.6 0.1 0.1 24 Ho 1.0 0.6 0.2 0.2 0.2 0.6 0.1 0.1 25 Ho 1.0 0.6 0.7 — — 0.7 0.1 0.1 26 Ho 1.0 0.6 — 0.7 — 0.7 0.1 0.1 27 Ho 1.0 0.6 — — 0.7 0.7 0.1 0.1 28 Ho 1.0 0.6 0.2 0.1 0.4 0.7 0.1 0.1 29 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0 0.1 Li₂O—: Li₂O—BaO—TiO₂—SiO₂ (unit: wt %)

TABLE 1-2 Rare-earth Sample (Re₂O₃) Total Number Element Content MgO Mn₂O₃ V₂O₅ Cr₂O₃ Content MoO₃ Li₂O— 30 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0.025 0.1 31 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0.05 0.1 32 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0.1 0.1 33 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0.2 0.1 34 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0.3 0.1 35 Ho 1.0 0.6 0.15 0.05 — 0.2 0.1 0.1 36 Ho 0 0.6 0.15 0.05 — 0.2 0.1 0.1 37 Ho 0.25 0.6 0.15 0.05 — 0.2 0.1 0.1 38 Ho 0.5 0.6 0.15 0.05 — 0.2 0.1 0.1 39 Ho 1.0 0.6 0.15 0.05 — 0.2 0.1 0.1 40 Ho 1.5 0.6 0.15 0.05 — 0.2 0.1 0.1 41 Ho 2.0 0.6 0.15 0.05 — 0.2 0.1 0.1 42 Ho 4.0 0.6 0.15 0.05 — 0.2 0.1 0.1 43 Sm 0.25 0.8 0.15 0.05 — 0.2 0.1 0.1 44 Sm 0.75 0.8 0.15 0.05 — 0.2 0.1 0.1 45 Eu 0.75 0.8 0.15 0.05 — 0.2 0.1 0.1 46 Gd 0.75 0.8 0.15 0.05 — 0.2 0.1 0.1 47 Tb 0.75 0.8 0.15 0.05 — 0.2 0.1 0.1 48 Dy 0.75 0.8 0.15 0.05 — 0.2 0.1 0.1 49 Er 0.75 0.4 0.15 0.05 — 0.2 0.1 0.1 50 Tm 0.75 0.4 0.15 0.05 — 0.2 0.1 0.1 51 Yb 0.75 0.4 0.15 0.05 — 0.2 0.1 0.1 52 Yb 1.0 0.4 0.15 0.05 — 0.2 0.1 0.1 53 Y 1.0 0.4 0.15 0.05 — 0.2 0.1 0.1 54 Ho/Dy 0.5/0.5 0.6 0.15 0.05 — 0.2 0.1 0.1 55 Ho/Dy/Yb 0.5/0.5/0.5 0.6 0.15 0.05 — 0.2 0.1 0.1 56 Sm/Ho/Yb 0.2/0.5/0.1 0.6 0.15 0.05 — 0.2 0.1 0.1 57 Sm/Yb 0.5/1.0 0.6 0.15 0.05 — 0.2 0.1 0.1 58 Ho 1 0 0.15 0.05 — 0.2 0.1 0.1 Li₂O—: Li₂O—BaO—TiO₂—SiO₂ (unit: wt %)

TABLE 1-3 RE Sample (Re₂O₃) Total B₂O₃—MO—SiO₂ Total No Elmt Cnt MgO Mn₂O V₂O Cr₂O₃ Content MoO₃ Li₂O— M B₂O₃ SiO₂ Mo Content 59 Ho 1.0 0.2 0.15 0.05 — 0.2 0.1 0.1 — — — — — 60 Ho 1.0 1.5 0.15 0.05 — 0.2 0.1 0.1 — — — — — 61 Ho 1.0 2.0 0.15 0.05 — 0.2 0.1 0.1 — — — — — 62 Ho 1.0 0.6 0.15 0.05 — 0.2 0.1 0 — — — — — 63 Ho 1.0 0.6 0.15 0.05 — 0.2 0.1 0.05 — — — — — 64 Ho 1.0 0.6 0.15 0.05 — 0.2 0.1 0.5 — — — — — 65 Ho 1.0 0.6 0.15 0.05 — 0.2 0.1 1.0 — — — — — 66 Ho 1.0 0.6 0.15 0.05 — 0.2 0.1 2.0 — — — — — 67 Ho 1.0 0.5 0.15 0.05 0.2 0.4 0.05 — Ca 15 65 20 0 68 Ho 1.0 0.5 0.15 0.05 0.2 0.4 0.05 — Ca 15 65 20 0.05 69 Ho 1.0 0.5 0.15 0.05 0.2 0.4 0.05 — Ca 15 65 20 2.00 70 Ho 1.0 0.5 0.15 0.05 0.2 0.4 0.05 — Ca 15 65 20 5.00 71 Ho 1.0 0.5 0.15 0.05 0.2 0.4 0.05 — Ca 15 65 20 10.00 72 Ho 1.0 0.5 0.15 0.05 0.2 0.4 0.05 — Ca 95 4 1 1.00 73 Ho 1.0 0.5 0.15 0.05 0.2 0.4 0.05 — Ca 90 9 1 1.00 74 Ho 1.0 0.5 0.15 0.05 0.2 0.4 0.05 — Ca 90 1 9 1.00 75 Ho 1.0 0.5 0.15 0.05 0.2 0.4 0.05 — Ca 50 50 0 1.00 76 Ho 1.0 0.5 0.15 0.05 0.2 0.4 0.05 — Ca 20 70 10 1.00 77 Ho 1.0 0.5 0.15 0.05 0.2 0.4 0.05 — Ca 19 80 1 1.00 78 Ho 1.0 0.5 0.15 0.05 0.2 0.4 0.05 — Ca 1 80 19 1.00 79 Ho 1.0 0.5 0.15 0.05 0.2 0.4 0.05 — Ca 4 95 1 1.00 80 Ho 1.0 0.5 0.15 0.05 0.2 0.4 0.05 — Ca 1 39 60 1.00 81 Ho 1.0 0.5 0.15 0.05 0.2 0.4 0.05 — Ca 29 1 70 1.00 82 Ho 1.0 0.5 0.15 0.05 0.2 0.4 0.05 — Ca 4 5 95 1.00 83 Ho 1.0 0.5 0.15 0.05 0.2 0.4 0.05 — Ca 20 30 50 1.00 Li₂O—: Li₂O—BaO—TiO₂—SiO₂ (unit: wt %)

TABLE 1-4 RE Sample (Re₂O₃) Ttl Ttl B₂O₃—MO—SiO₂ Ttl No. Elmt Cnt MgO Mn₂O₃ V₂O₅ Cr₂O₃ α Cnt MoO₃ WO₃ Cnt M B₂O₃ SiO₂ Mo Cnt 84 Ho 1.0 0.6 0.02 — — 0.01 0.03 0.05 0.05 0.1 Ba 15 65 20 1.00 85 Ho 1.0 0.6 — 0.02 — 0.01 0.03 0.05 0.05 0.1 Ba 15 65 20 1.00 86 Ho 1.0 0.6 — — 0.02 0.01 0.03 0.05 0.05 0.1 Ba 15 65 20 1.00 87 Ho 1.0 0.6 0.03 — — 0.01 0.04 0.05 0.05 0.1 Ca 15 65 20 1.00 88 Ho 1.0 0.6 — 0.03 — 0.01 0.04 0.05 0.05 0.1 Ca 15 65 20 1.00 89 Ho 1.0 0.6 — — 0.03 0.01 0.04 0.05 0.05 0.1 Ca 15 65 20 1.00 90 Ho 1.0 0.6 0.01 0.02 — 0.01 0.04 0.05 0.05 0.1 Sr 15 65 20 1.00 91 Ho 1.0 0.6 0.05 0.02 — 0.01 0.08 0.05 0.05 0.1 Sr 15 65 20 1.00 92 Ho 1.0 0.6 0.05 — 0.1 0.01 0.16 0.05 0.05 0.1 Sr 15 65 20 1.00 93 Ho 1.0 0.6 0.05 0.01 0.1 0.01 0.17 0.05 0.05 0.1 Sr 15 65 20 1.00 94 Ho 1.0 0.6 0.1 0.05 0.1 0.1 0.35 0.05 0.05 0.1 Mg 15 65 20 1.00 95 Ho 1.0 0.6 0.1 0.1 0.1 0.1 0.4 0.05 0.05 0.1 Mg 15 65 20 1.00 96 Ho 1.0 0.6 0.3 — — 0.1 0.4 0.05 0.05 0.1 Mg 15 65 20 1.00 97 Ho 1.0 0.6 — 0.3 — 0.1 0.4 0.05 0.05 0.1 Mg 15 65 20 1.00 98 Ho 1.0 0.6 — — 0.3 0.1 0.4 0.05 0.05 0.1 Mg 15 65 20 1.00 99 Ho 1.0 0.6 0.6 — — 0.4 1 0.05 0.05 0.1 Zn 15 85 20 1.00 100 Ho 1.0 0.6 — 0.6 — 0.4 1 0.05 0.05 0.1 Zn 35 65 20 1.00 101 Ho 1.0 0.6 — — 0.6 0.4 1 0.05 0.05 0.1 Zn 15 65 20 1.00 102 Ho 1.0 0.6 0.3 0.3 — 0.4 1 0.05 0.05 0.1 Ba 15 65 20 1.00 103 Ho 1.0 0.6 0.3 — 0.3 0.4 1 0.05 0.05 0.1 Ba 15 65 20 1.00 104 Ho 1.0 0.6 — 0.3 0.3 0.4 1 0.05 0.05 0.1 Ba 15 65 20 1.00 105 Ho 1.0 0.6 0.2 — 0.4 0.4 1 0.05 0.05 0.1 Ba 15 65 20 1.00 106 Ho 1.0 0.6 0.1 — 0.5 0.4 1 0.05 0.05 0.1 Ba 15 65 20 1.00 107 Ho 1.0 0.6 0.2 0.2 0.2 0.4 1 0.05 0.05 0.1 Ba 15 65 20 1.00 108 Ho 1.0 0.6 0.7 — — 0.6 1.3 0.05 0.05 0.1 Ba/Ca 15 65 10/10 1.00 109 Ho 1.0 0.6 — 0.7 — 0.6 1.3 0.05 0.05 0.1 Ba/Ca 15 65 10/10 1.00 110 Ho 1.0 0.6 — — 0.7 0.6 1.3 0.05 0.05 0.1 Ba/Ca 15 65 10/10 1.00  α: FeO—NiO—CuO (unit: mol %)

TABLE 1-5 Rare-earth Sample (Re₂O₃) Total Total Number Element Content MgO Mn₂O₃ V₂O₅ Cr₂O₃ Content MoO₃ WO₃ Content LiO— SiO₂ 111 Ho 1.0 0.6 0.15 0.05 — 0.2 0.05 — 0.05 — 0.0 112 Ho 1.0 0.6 0.15 0.05 — 0.2 0.05 — 0.05 — 0.2 113 Ho 1.0 0.6 0.15 0.05 — 0.2 0.05 — 0.05 — 1.0 114 Ho 1.0 0.6 0.15 0.05 — 0.2 0.05 — 0.05 — 4.0 l15 Ho 1.0 0.6 0.15 0.05 — 0.2 0.05 — 0.05 — 5.0 l16 Ho 1.0 0.6 0.05 0.1 0.1 0.25 — 0 0 0.1 — 117 Ho 1.0 0.6 0.05 0.1 0.1 0.25 — 0.025 0.025 0.1 — 118 Ho 1.0 0.6 0.05 0.1 0.1 0.25 — 0.05 0.05 0.1 — 119 Ho 1.0 0.6 0.05 0.1 0.1 0.25 — 0.1 0.1 0.1 — 120 Ho 1.0 0.6 0.05 0.1 0.1 0.25 — 0.2 0.2 0.1 — 121 Ho 1.0 0.6 0.05 0.1 0.1 0.25 — 0.3 0.3 0.1 — 122 Ho 1.0 0.6 0.05 0.1 0.1 0.25 — 0.4 0.4 0.1 — 123 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0 0 0 0.1 — 124 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0.01 0.01 0.025 0.1 — 125 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0.02 0.02 0.04 0.1 — 126 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0 0.05 0.05 0.1 — 127 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0.025 0.05 0.075 0.1 — 128 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0.05 0.05 0.1 0.1 — 129 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0.1 0.05 0.15 0.1 — 130 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0.2 0.05 0.25 0.1 — 131 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0.3 0.05 0.35 0.1 — 132 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0.05 0 0.05 0.1 — 133 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0.05 0.025 0.075 0.1 — 134 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0.05 0.05 0.1 0.1 — 135 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0.05 0.1 0.15 0.1 — 136 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0.05 0.2 0.25 0.1 — 137 Ho 1.0 0.6 0.05 0.1 0.1 0.25 0.05 0.3 0.35 0.1 — Li₂O—: Li₂O—BaO—TiO₂—SiO₂ (unit wt %)

TABLE 1-6 RE Sample (Re₂O₃) Ttl Li₂O—SiO₂—MO Ttl No. Elmt Cnt MgO Mn₂O₃ V₂O₃ α Cnt MoO₃ WO₃ Cnt M Li₂O SiO₂ Mo Cnt 138 Ho 1.0 0.6 0.15 0.05 0.1 0.3 0.05 0.05 0.1 Ca 15 65 20 0 139 Ho 1.0 0.6 0.15 0.05 0.1 0.3 0.05 0.05 0.1 Ca 15 65 20 0.05 140 Ho 1.0 0.6 0.15 0.05 0.1 0.3 0.05 0.05 0.1 Ca 15 65 20 2 141 Ho 1.0 0.6 0.15 0.05 0.1 0.3 0.05 0.05 0.1 Ca 15 65 20 5 142 Ho 1.0 0.6 0.15 0.05 0.1 0.3 0.05 0.05 0.1 Ca 15 65 20 10 143 Ho 1.0 0.6 0.15 0.05 0.1 0.3 0.05 0.05 0.1 Ca 95 4 1 1 144 Ho 1.0 0.6 0.15 0.05 0.1 0.3 0.05 0.05 0.1 Ca 90 9 1 1 145 Ho 1.0 0.6 0.15 0.05 0.1 0.3 0.05 0.05 0.1 Ca 89 1 10 1 146 Ho 1.0 0.6 0.15 0.05 0.1 0.3 0.05 0.05 0.1 Ca 50 50 0 1 147 Ho 1.0 0.6 0.15 0.05 0.1 0.3 0.05 0.05 0.1 Ca 20 70 10 1 148 Ho 1.0 0.6 0.15 0.05 0.1 0.3 0.05 0.05 0.1 Ca 5 94 1 1 149 Ho 1.0 0.6 0.15 0.05 0.1 0.3 0.05 0.05 0.1 Ca 1 94 5 1 150 Ho 1.0 0.6 0.15 0.05 0.1 0.3 0.05 0.05 0.1 Ca 4 95 1 1 151 Ho 1.0 0.6 0.15 0.05 0.1 0.3 0.05 0.05 0.1 Ca 1 79 20 1 152 Ho 1.0 0.6 0.15 0.05 0.1 0.3 0.05 0.05 0.1 Ca 19 1 60 1 153 Ho 1.0 0.6 0.15 0.05 0.1 0.3 0.05 0.05 0.1 Ca 4 5 95 1 154 Ho 1.0 0.6 0.15 0.05 0.1 0.3 0.05 0.05 0.1 Ca 20 30 50 1  α: FeO—NiO—CuO (unit: mol %)

Thereafter, the dried ceramic slurry was ground and then calcined in air at about 800° C. for 3 hours. The calcined slurry was then disaggregated by a wet method in a ball mill added with ethanol for about 10 hours. Next, the disaggregated ceramic slurry was dried by being heated at about 200° C. for 5 hours, thereby obtaining the powder of the calcined ceramic slurry.

In a following step, a dielectric ceramic slurry was obtained by mixing and grinding 1000 g (100 parts by weight) of the powder of the dielectric ceramic slurry, 15 wt % of an organic binder and 50 wt % of water in a ball mill, wherein the organic binder includes acrylic ester polymer, glycerin, and a solution of condensed phosphate.

Next, the dielectric slurry was subjected to a vacuum air separator to remove air bubbles therefrom and formed into a thin film coated on a polyester film by using a reverse roll coater. Thus produced ceramic thin film on the polyester film was heated and dried at about 100° C. and then diced to thereby obtain square ceramic green sheets having a thickness of about 5 μm and a size of about 10 cm×10 cm.

Meanwhile, 0.9 g of ethyl cellulose dissolved in 9.1 g of butyl carbitol and 10 g of Nickel powder having an average diameter of about 0.5 μm were loaded and stirred in a stirrer for 10 hours to form a conductive paste for use in forming internal electrodes of ceramic capacitors. Thereafter, the conductive paste was printed on the prepared ceramic green sheets to form conductive patterns thereon and then the printed conductive paste was dried.

Subsequently, ten ceramic green sheets having the conductive patterns thereon were stacked against each other with the conductive patterns facing upward, thereby forming a laminated body. Every two neighboring sheets were disposed in such a manner that the conductive patterns provided thereon were shifted by one half of a pattern size along the length direction. The laminated body also included one or more ceramic dummy sheets stacked against each of the uppermost and the lowermost ceramic green sheets having conductive patterns thereon, the ceramic dummy sheets representing ceramic green sheets without having conductive patterns thereon.

Next, the laminated body was pressed with a load of about 40 tons at about 50° C. along the stacking direction of the ceramic sheets in the laminated body. Afterwards, the pressed laminated body was diced into a multiplicity of chip shaped ceramic bodies having a size of about 3.2 mm×1.6 mm.

Thereafter, Ni external electrodes were formed at two opposite sides of each chip shaped ceramic body by, e.g., a dipping method, one end portion of each of the internal electrodes being exposed to one of the two opposite sides of each chip shaped ceramic body. Then, the chip shaped ceramic bodies were loaded into a furnace capable of controlling an atmosphere therein and the organic binder contained in the loaded ceramic bodies was removed by heating the furnace in an N₂ atmosphere. Then, the binder-removed chip shaped ceramic bodies were sintered at about 1300° C. in a non-oxidative atmosphere with oxygen partial pressure being in 10⁻⁵ to 10⁻⁸ atm order range. Thereafter, the sintered chip-shaped ceramic bodies were re-oxidized in an oxidative atmosphere to thereby obtain multilayer ceramic capacitors as shown in FIG. 1., wherein reference numerals 10, 12 and 14 represent dielectric layers, internal electrodes and external electrodes, respectively.

Tables 2-1 to 2-6 exhibit a measurement result of electrical characteristics obtained from the thus produced multilayer ceramic capacitors, wherein a thickness of each dielectric layer incorporated in the capacitors was about 3 μm.

The electrical characteristics of the multilayer ceramic capacitors were obtained as follows.

(A) Relative permittivity or dielectric constant ε_(s) was computed based on a facing area of a pair of neighboring internal electrodes, a thickness of a dielectric layer positioned between the pair of neighboring internal electrodes, and the capacitance of a multilayer ceramic capacitor obtained under the condition of applying at 20° C. a voltage of 1.0 V (root mean square value) with a frequency of 1 kHz.

(B) Dielectric loss tanδ (%) was obtained under the same condition as established for measuring the permittivity cited above.

(C) resistivity (Ωcm) was acquired by measuring a resistance between a pair of external electrodes after DC 25 V was applied for 60 seconds at 20° C. The number following “E” in the notation of a resistivity value presented in the accompanying Tables 2-1 to 2-6 represents an order. For instance, 4.8 E+12 represents 4.8×10¹².

(D) Accelerated life (second) was obtained by measuring time period until an insulation resistivity (ρ) becomes 1×10¹⁰ Ωcm in a DC electric field of 20 V/μm at 150° C.

(E) Capacitance variation ΔC/C₂₅ (%) was obtained by measuring capacitances at −55° C., +25° C. and +125° C. in a thermostatic (or constant temperature) oven under the condition of applying a voltage of 1 V (rms value) with a frequency of 1 kHz, wherein C₂₅ represents a capacitance at 25° C. and Δ C represents the difference between C₂₅ and a capacitance measured at −55° C. or 125° C.

TABLE 2-1 Resistivity Capacitance Sintering (Ω cm) at Variation Accelerated Sample Temperature Room ΔC/C₂₅ (%) Life Number (° C.) Permittivity Tan δ (%) Temperature −55° C. 125° C. (sec)  1 1300 3400 3.3 4.8E+12 −12.0 −14.5 140,400  2 1300 3320 3.4 9.8E+12 −13.4 −13.9 162,000  3 1300 3680 3.6 3.1E+12 −12.5 −14.4  86,400  4 1300 3350 3.1 2.2E+12 −11.2 −13.8 244,800  5 1300 3310 3.0 1.1E+12 −11.5 −14.1 320,400  6 1300 3500 3.4 1.2E+12 −12.2 −14.5 235,400  7 1300 3440 3.3 5.5E+12 −12.1 −13.8 277,200  8 1300 3290 3.1 6.4E+12 −12.4 −13.8 295,200  9 1300 3410 3.3 7.8E+12 −12.9 −13.9 248,400  10 1300 3380 3.1 3.1E+12 −13.3 −14.1 349,200  11 1300 3150 2.8 3.1E+12 −11.2 −13.3 432,000  12 1300 3080 2.4 9.2E+11 −11.0 −14.1 560,100  13 1300 3190 2.5 3.6E+12 −12.0 −14.4 420,400  14 1300 3010 2.9 4.5E+11 −14.5 −14.1 623,800  15 1300 3620 3.5 2.7E+11 −14.8 −15.0 220,800  16 1300 3100 2.9 4.3E+12 −10.9 −12.4 1,080,400    17 1300 3030 2.4 5.5E+12 −11.3 −12.9 2,875,000    18 1300 3280 3.0 1.2E+12 −12.3 −13.5 328,900  19 1300 3080 2.6 6.5E+12 −11.5 −13.2 3,498,900    20 1300 3140 2.9 9.6E+12 −13.4 −14.3 1,094,900    21 1300 3050 2.9 3.1E+12 −13.4 −13.9 1,947,600    22 1300 3090 3.0 5.5E+12 −12.8 −13.8 335,400  23 1300 3170 3.1 2.5E+12 −10.8 −12.9 298,400  24 1300 3010 2.5 5.9E+12 −12.7 −14.8 1,048,500    25 1300 2950 2.0 2.9E+12 −12.1 −13.9 829,000  26 1300 2610 2.9 3.9E+11 −12.6 −14.5 1,253,400    27 1300 2950 3.1 3.9E+11 −12.2 −15.5 145,900  28 1300 3030 2.3 3.7E+12 −11.9 −14.3 2,087,500    29 1300 3250 3.0 4.0E+12 −13.3 −14.1 179,000

TABLE 2-2 Resistivity Capacitance Sintering (Ω cm) at Variation Accelerated Sample Temperature Room ΔC/C₂₅ (%) Life Number (° C.) Permittivity Tan δ (%) Temperature −55° C. 125° C. (sec)  30 1300 3310 3.1 3.5E+12 −13.9 −13.3 353,900  31 1300 3420 3.2 5.9E+11 −14.1 −13.3 819,400  32 1300 3140 3.4 2.2E+11 −13.9 −13.4 1,043,500  33 1300 3520 3.5 1.0E+11 −13.2 −12.8 1,567,800  34 1300 3740 5.2 3.1E+10 −17.2 −8.2 3,255,800  35 1300 3390 3.0 5.5E+12 −13.9 −14.3 810,400  36 1300 3980 4.4 9.2E+11 −13.9 −17.1 18,000  37 1300 3470 3.5 3.2E+12 −14.4 −14.5 221,600  38 1300 3320 3.3 3.9E+12 −13.3 −14.4 498,700  39 1300 3190 2.9 6.4E+12 −14.1 −14.5 925,800  40 1300 3040 2.8 2.2E+12 −14.9 −14.4 1,245,300  41 1300 Incapable of obtaining a sintered ceramic with high density  42 1300 incapable of obtaining a sintered ceramic with high density  43 1300 3590 3.5 2.9E+11 −14.5 −14.9 210,900  44 1300 3310 3.5 3.1E+11 −14.4 −15.0 348,000  45 1300 3190 3.2 8.1E+12 −13.3 −14.8 287,100  46 1300 3350 3.3 3.0E+12 −14.1 −14.8 453,900  47 1300 3300 3.4 3.2E+12 −14.1 −14.7 558,900  48 1300 3410 3.5 6.1E+12 −14.4 −14.9 923,400  49 1300 3090 2.8 8.2E+12 −13.7 −13.9 498,900  50 1300 3090 2.8 7.9E+12 −14.1 −13.8 348,500  51 1300 3110 2.6 3.5E+12 −14.4 −14.1 298,100  52 1300 3030 2.6 3.2E+12 −13.9 −14.2 340,400  53 1300 3350 3.2 4.1E+12 −14.4 −14.4 498,200  54 1300 3410 3.3 3.0E+12 −13.9 −14.1 598,100  55 1300 3320 3.3 2.1E+12 −14.4 −14.9 440,400  56 1300 3510 3.4 8.1E+12 −13.9 −14.9 784,300  57 1300 3280 3.3 3.9E+12 −13.4 −14.9 340,000  58 1300 7590 8.8 4.1E+14 −45.2 12.4 285,600

TABLE 2-3 Resistivity Capacitance Sintering (Ω cm) at Variation Accelerated Sample Temperature Room ΔC/C₂₅ (%) Life Number (° C.) Permittivity Tan δ (%) Temperature −55° C. 125° C. (sec)  59 1300 3590 3.5 3.2E+12 −14.9 −13.2 697,200  60 1300 3020 3.0 3.9E+12 −13.0 −15.0 298,500  61 1300 2950 2.2 2.1E+13 −13.1 −17.2 123,000  62 1300 3690 4.2 4.4E+13 13.3 −15.0  12,000  63 1300 3370 3.3 9.1E+12 −13.9 −14.4 492,100  64 1300 3080 3.0 3.0E+13 −12.3 −14.1 318,000  65 1300 3010 2.5 3.1E+13 −13.0 −13.9 259,100  66 1300 2790 2.0 4.9E+13 −13.3 −14.4  2,300  67 1300 Incapable of obtaining a sintered ceramic with high density  68 1300 3400 3.5 2.1E+12 −14.1 −14.5 567,800  69 1280 3290 2.5 3.6E+13 −12.5 −14.4 439,000  70 1280 3060 3.0 3.5E+13 −13.4 −13.2 650,900  71 1280 2480 2.4 5.0E+13 −13.5 −14.1  4,500  72 1300 Incapable of obtaining a sintered ceramic with high density  73 1300 3290 3.4 4.4E+13 −14.4 13.9 875,600  74 1300 3350 3.5 5.3E+13 −13.5 −13.4 764,900  75 1300 — — 3.5E+13 — —  76 1300 3180 3.3 5.3E+13 −14.4 −13.3 485,900  77 1300 3080 3.2 5.9E+13 −13.1 −13.5 354,800  78 1300 3430 3.3 8.2E+13 −12.8 −15.0 298,700  79 1300 Incapable of obtaining a sintered ceramic with high density  80 1300 3200 3.5 3.5E+13 −14.5 −14.8 498,500  81 1300 3420 3.3 7.1E+13 −14.6 −15.0 429,800  82 1300 Incapable of obtaining a sintered ceramic with high density  83 1300 3310 3.5 5.7E+13 −13.8 −14.3 656,700

TABLE 2-4 Resistivity Capacitance Sintering (Ω cm) at Variation Accelerated Sample Temperature Room ΔC/C₂₅ (%) Life Number (° C.) Permittivity Tan δ (%) Temperature −55° C. 125° C. (sec)  84 1300 3002 3.25 1.46E+12  −11.4 −11.5  29,500  85 1300 3613 2.96 4.88E+10  −14.7 −12.1  19,700  86 1300 3669 2.89 1.49E+12  −11.9 −13.4 138,300  87 1300 3300 2.59 9.28E+11  −14.8 −13.7 257,100  88 1300 3281 2.86 1.92E+12  −11.2 −11.6 480,200  89 1300 3707 2.50 1.99E+12  −14.9 −12.1 343,300  90 1300 3653 3.01 1.73E+12  −12.3 −14.6 337,400  91 1300 3355 2.75 8.04E+11  −11.1 −13.7 207,800  92 1300 3636 3.19 1.18E+12  −13.8 −13.6 306,600  93 1300 3013 3.20 1.96E+12  −12.8 −12.4 351,000  94 1300 3540 2.72 5.21E+11  −12.0 −12.2 300,900  95 1300 3141 2.63 1.94E+12  −11.3 −13.4 429,200  96 1300 3084 3.29 5.23E+11  −14.1 −12.3 213,200  97 1300 3402 2.55 8.61E+11  −13.1 −14.6 449,900  98 1300 3522 2.74 1.64E+12  −13.5 −12.4 263,300  99 1300 3547 3.28 6.36E+11  −13.5 −14.5 406,700 100 1300 3611 2.92 5.97E+11  −13.1 −14.9 401,800 101 1300 3105 3.32 6.00E+11  −13.6 −13.3 351,400 102 1300 3422 3.08 1.54E+12  −12.6 −13.6 206,800 103 1300 3037 2.78 1.09E+12  −12.1 −11.2 479,700 104 1300 3753 3.19 9.37E+11  −14.0 −11.7 475,400 105 1300 3214 3.20 4.03E+11  −14.8 −14.7 404,800 106 1300 3555 3.13 1.41E+12  −14.8 −11.3 228,500 107 1300 3269 2.56 1.18E+12  −14.4 −14.1 279,400 108 1300 2386 2.95 1.29E+11  −14.7 −14.4 320,500 109 1300 2865 2.72 2.11E+11  −13.1 −12.6 496,700 110 1300 2187 2.76 1.53E+12  −14.2 −13.1 167,500

TABLE 2-5 Resistivity Capacitance Sintering (Ω cm) at Variation Accelerated Sample Temperature Room ΔC/C₂₅ (%) Life Number (° C.) Permittivity Tan δ (%) Temperature −55° C. 125° C. (sec) 111 1300 Incapable of obtaining a sintered ceramic with high density 112 1300 3490 3.5 4.3E+12 −14.5 −14.8 875,100 113 1300 3120 2.9 2.7E+13 −14.1 −14.6 547,800 114 1300 3010 2.3 1.5E+13 −13.4 −12.8 564,000 115 1300 2690 2.8 5.3E+13 −13.5 −14.6  5,600 116 1300 3420 3.1 5.5E+12 −13.4 −15.6 153,800 117 1300 3330 3.1 3.5E+12 −13.9 −13.3 224,900 118 1300 3410 3.3 2.8E+12 −14.1 −13.3 332,700 119 1300 3410 3.4 3.9E+11 −13.1 −13.9 983,400 120 1300 3470 3.3 1.2E+11 −13.2 −12.8 1,173,800   121 1300 3520 3.3 1.4E+11 −14.6 −11.7 2,138,000   122 1300 3730 4.3 4.7E+10 −17.2 −9.6 3,278,000   123 1300 3250 3.0 4.0E+12 −13.3 −14.1 179,000 124 1300 3320 3.1 5.8E+12 −13.5 −14.2 237,000 125 1300 3350 3.2 8.2E+12 −13.8 −13.8 279,000 126 1300 3410 3.3 2.8E+12 −14.1 −13.3 332,700 127 1300 3450 3.3 1.8E+12 −14.0 −13.4 402,500 128 1300 3500 3.4 9.9E+11 −13.9 −13.2 869,800 129 1300 3540 3.5 7.6E+11 −13.5 −13.1 1,115,800   130 1300 3610 3.5 8.7E+10 −13.3 −12.6 1,408,900   131 1300 3840 6.2 5.4E+10 −18.0 −7.3 3,384,600   132 1300 3100 2.9 4.6E+12 −13.2 −14.3 132,000 133 1300 3110 3.1 5.3E+12 −13.4 −14.4 242,000 134 1300 3350 3.2 5.6E+12 −13.6 −14.2 530,000 135 1300 3420 3.4 5.6E+12 −13.9 −13.8 889,000 136 1300 3550 3.5 5.6E+12 −13.9 −13.2 1,086,000   137 1300 3680 4.7 5.6E+12 −14.9 −10.5 2,532,000  

TABLE 2-6 Resistivity Capacitance Sintering (Ω cm) at Variation Accelerated Sample Temperature Room ΔC/C₂₅ (%) Life Number (° C.) Permittivity Tan δ (%) Temperature −55° C. 125° C. (sec) 138 1300 Incapable of obtaining a sintered ceramic with high density 139 1300 3314 2.82 7.36E+11 −11.3 −11.0 319,400 140 1300 3678 3.17 1.20E+12 −14.3  −12.8 469,100 141 1300 3452 2.82 6.61E+11 −14.3  −11.2 425,300 142 1300 Incapable of obtaining a sintered ceramic with high density 143 1300 2843 2.87 8.17E+11 −14.4 −12.8  30,900 144 1300 3387 2.54 1.16E+12 −12.8  −14.0 377,900 145 1300 3720 3.31 1.80E+12 −11.4  −14.3 309,200 146 1300 3527 3.36 8.10E+11 −11.1  −11.9 376,500 147 1300 3706 3.18 7.88E+10 −12.4  −12.8 470,600 148 1300 3671 3.29 5.91E+11 −11.8  −14.2 433,700 149 1300 3338 2.75 3.06E+11 −13.5  −13.6 224,900 150 1300 Incapable of obtaining a sintered ceramic with high density 151 1300 3161 3.16 7.62E+11 −12.8 −11.4 471,800 152 1300 3765 2.89 1.57E+12 −11.9  −12.3 299,600 153 1300 Incapable of obtaining a sintered ceramic with high density 154 1300 3786 2.73 4.64E+11 −14.4 −13.1 330,200

As clearly seen from Tables 1-1 to 1-6 and Tables 2-1 to 2-6, multilayer ceramic capacitors with highly improved reliability having relative permittivity ε_(s) equal to or greater than 3000, capacitance variation ΔC/C₂₅ within the range from −15% to +15% at temperatures ranging from −55° C. to +125° C., tan δ of 3.5% or less and accelerated life of 200,000 seconds or greater could be obtained from the above samples sintered in a non-oxidative atmosphere even at a temperature of 1300° C. or lower in accordance with the present invention.

However, samples 1 to 3, 25 to 27, 29, 34, 36, 41, 42 58, 61, 62, 66, 67, 71, 72, 75, 79, 82, 84, 85, 86, 108 to 111, 115, 116, 122, 123, 131, 137, 138, 142, 143, 146, 150, and 153 (marked with “” at the column of sample numbers in Tables) could not satisfy the above-specified electrical characteristics. Therefore, it appears that such samples fall outside a preferable compositional range of the present invention.

The reasons why the preferable compositional range for the dielectric ceramics in accordance with the present invention should be limited to certain values will now be described. In Tables 1-1 to 1-6, the amount of oxides of Ba and Ti was 100 mol % in terms of BaTiO₃ (i.e., assuming Ba and Ti are in the form of BaTiO₃).

First, when the content of an oxide of a rare-earth element represented by Re (Re is selected, e.g., from the group consisting of Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Y) is 0 mol % in terms of Re₂O₃ (i.e., assuming the oxide of Re is in the form of Re₂O₃) as in the sample 36, the capacitance variation ΔC/C₂₅ of a produced multilayer ceramic capacitor goes beyond the range from −15% to +15% when temperature varies from −55° C. to +125° C. or a desired accelerated life may not be attained; whereas when the oxide of Re is set to be 0.25 mol % in terms of Re₂O₃ as in sample 37, the desired electrical characteristics can be successfully obtained.

Further, when the content of the oxide of the rare-earth element Re is equal to or greater than 2.0 mol % in terms of Re₂O₃ as in the samples 41 and 42, highly densified ceramic bodies may not be obtained by the sintering at 1300° C.; whereas when the oxide of the rare-earth element Re is set to be 1.5 mol % in terms of Re₂O₃ as in sample 40, the desired electrical characteristics can be successfully obtained.

Accordingly, the preferable range of the content of oxide of the rare-earth element Re is from 0.25 to 1.5 mol % in terms of Re₂O₃.

It is noted that same effects can be produced regardless of whether a single rare-earth element is used as in samples 43 to 53, or two or more of rare-earth elements are used together as in samples 54 to 57 as long as the above-described preferable content range of the rare-earth element Re is satisfied.

When the content of an oxide of Mg is 0 mol % in terms of MgO as in the sample 58, the capacitance variation ΔC/C₂₅ of a produced multilayer ceramic capacitor may exceed the range from −15% to +15% when the temperature varies from −55° C. to +125° C., or tanδ may be deteriorated over 3.5%; whereas when the content of the oxide of Mg is be 0.2 mol % in terms of MgO as in sample 59, the desired electrical characteristics can be successfully obtained.

In addition, when the content of the oxide of Mg is 2.0 mol % in terms of MgO as in the sample 61, the relative permittivity of the produced multilayer ceramic capacitors may become equal to or less than 3000 and the desired accelerated life cannot be obtained. However, when the content of the oxide of Mg is set to be 1.5 mol % in terms of MgO as in sample 60, the desired electrical characteristics can be successfully obtained.

Accordingly, the content of the oxide of Mg desirably ranges from 0.2 to 1.5 mol % in terms of MgO.

When the content of an oxide of each element Mn, V or Cr is 0.02 mol % in terms of Mn₂O₃, V₂O₅ or Cr₂O₃, as in the samples 1 to 3, the desired accelerated life of the produced multilayer ceramic capacitors may not be obtained; whereas when the total content of the oxides of Mn, V and Cr is set to be 0.03 mol % in terms of Mn₂O₃, V₂O₅ and Cr₂O₃, as in the samples 4 to 6, the desired characteristics can be successfully attained.

Further, when the content of an oxide of Mn, V or Cr is 0.7 mol % in terms of Mn₂O₃, V₂O₅ or Cr₂O₃, as in the samples 25 to 27, the relative permittivity of the capacitors becomes equal to or less than 3000. However, when the content of sum of the oxides of Mn, V and Cr is set to be 0.6 mol % in terms of Mn₂O₃, V₂O₅ and Cr₂O₃, as in samples 22 to 24, the desired characteristics can be successfully attained.

Accordingly, it is preferable that the total amount of oxides of Mn, V and Cr ranges from 0.03 to 0.6 mol % in terms of Mn₂O₃, V₂O₅ and Cr₂O₃.

Further, it is to be noted that same effects can be obtained regardless of whether an oxide of one of the elements Mn, V and Cr is used along as in samples 4 to 6 and 13 to 18, or two or more thereof are used together as in samples 7 to 12 and 19 to 24 as long as the total content thereof satisfies the above specified range.

When the total content of oxides of Mo and W is 0 mol % in terms of MoO₃ and WO₃, as in the samples 29, 116 and 123, the desired accelerated life of the produced multilayer ceramic capacitors cannot be obtained. However, if the total content of oxides of Mo and W is set to be 0.025 mol % in terms of MoO₃ and WO₃, respectively, as in samples 30, 117 and 124, the desired characteristics can be successfully attained.

Further, when the content of oxides of Mo and W is greater than 0.25 mol % in terms of MoO₃ and WO₃, as in the samples 34, 122 and 137, the desired accelerated life may not be obtained or the capacitance variation ΔC/C₂₅ exceeds the range from −15 to +15% with the temperature varying from −55° C. to +125° C., or the tanδ may be deteriorated over 3.5. However, when the total content of oxides is set to be 0.25 mol %, as in samples 130 and 136, the desired electrical characteristics can be successfully obtained.

Accordingly, it is preferable that the total content of the oxides of Mo and W ranges from 0.025 to 0.25 mol % in terms of MoO₃ and WO₃.

Furthermore, same effects can be obtained regardless of whether the oxides of Mo and W are used separately as in samples 30 to 33 and 117 to 121, or used together as in samples 124 to 130 and 132 to 136.

The optimum range of the glass component varies depending on the constituents thereof.

First, in case the glass component is substantially formed of SiO₂ only, the optimum content of the glass component is as follows:

When the content of SiO₂ is 0.00 mol % as in sample 111, a highly densified ceramic body may not be obtained by the sintering process at 1300° C.; whereas when the content of SiO₂ is set to be 0.2 mol % as in sample 112, the desired electrical characteristics can be successfully obtained.

Further, when the content of SiO₂ is 5.0 mol % as in sample 115, the desired accelerated life may not be obtained; whereas when the content of SiO₂ is set to be 4.0 mol % as in sample 114, the desired electrical characteristics can be obtained.

Accordingly the content of the glass component mainly formed of SiO₂ preferably ranges from 0.20 mol % and 4 mol %.

In case the glass component including SiO₂ is composed of Li₂O—BaO—TiO₂—SiO₂, the optimum range of the content of Li₂O—BaO—TiO₂—SiO₂ preferably is determined as follows:

When the total content of glass component Li₂O—BaO—TiO₂—SiO₂ is 0 mol % as in the sample 62, tanδ of the produced capacitor may be deteriorated over 3.5% or the desired accelerated life may not be obtained; whereas when the content of the glass component Li₂O—BaO—TiO₂—SiO₂ is 0.05 mol % as in sample 63, the desired electrical characteristics can be successfully attained.

Further, when the content of the glass component Li₂O—BaO—TiO₂—SiO₂ is 2.0 mol % as in the sample 66, the relative permittivity of the produced multilayer ceramic capacitor may fall below 3000 or the desired accelerated life may not be attained; whereas when the content of the glass component Li₂O—BaO—TiO₂—SiO₂ is 1.0 mol % as in the sample 65, the desired electrical characteristics can be obtained.

Accordingly, the total content of the glass component Li₂O—BaO—TiO₂—SiO₂ is preferably between 0.05 and 1.0 wt % inclusive.

In case the glass component including SiO₂ is composed of B₂O₃—SiO₂-MO (MO used herein represents one or more oxides selected from the group of BaO, SrO, CaO, MgO and ZnO), the preferable composition of B₂O₃—SiO₂-MO for obtaining desired electrical characteristics is within the range surrounded by 6 lines formed by cyclically connecting 6 points A, B, C, D, E and F in that order shown in a triangular composition diagram of FIG. 2, wherein the triangular composition diagram exhibits a composition of B₂O₃—SiO₂-MO in terms of their mol %. The first point A represents a composition containing 1 mol % of B₂O₃, 80 mol % of SiO₂ and 19 mol % of MO, a second point B represents a composition including 1 mol % of B₂O₃, 39 mol % of SiO₂ and 60 mol % of MO. The third point C represents a composition containing 29 mol % of B₂O₃, 1 mol % of SiO₂ and 70 mol % of MO. The fourth point D represents a composition containing 90 mol % of B₂O₃, 1 mol % of SiO₂ and 9 mol % of MO. The fifth point E represents a composition containing 90 mol % of B₂O₃, 9 mol % of SiO₂ and 1 mol % of MO and the sixth point F represents a composition containing 19 mol % of B₂O₃, 80 mol % of SiO₂ and 1 mol % of MO. If a B₂O₃—SiO₂-Mo composition is within the range defined with 6 points described above as in samples 73, 74, 76 to 78, 80, 81 and 83, the desired electrical characteristics can be obtained. However, if the composition is out of the range not as in the samples 72, 75, 79 and 82, a highly densified ceramic body may not be attained at 1300° C.

Further, when the content of B₂O₃—SiO₂-MO is 0 wt % as in the sample 67, a highly densified ceramic body may not be obtained when sintered at 1300° C.; whereas when the content of B₂O₃—SiO₂-Mo is 0.05 wt % as in sample 68, the desired electrical characteristics can be successfully attained.

Still further, when the content of B₂O₃—SiO₂-Mo is 10.00 wt % as in the sample 71, the relative permittivity may become less than 3000 or the desired accelerated life may not be obtained; whereas when the content of B₂O₃—SiO₂-Mo is set to be 5.00 wt % as in sample 70, the desired electrical characteristics can be obtained.

Accordingly, the content of B₂O₃—SiO₂-Mo preferably ranges from 0.05 to 5.0 wt %.

When the glass component including SiO₂ is composed of Li₂O—SiO₂-MO (Mo used herein represents one or more oxides selected from the group consisting of BaO, SrO, CaO, MgO and ZnO), the preferable compositional range for Li₂O—SiO₂-MO is within the range surrounded by 6 lines formed by cyclically connecting 6 points G, H, I, J, K and L in that order as shown in a triangular composition diagram of FIG. 3, wherein the triangular diagram shows a compositional of Li₂O—SiO₂-MO in a unit of mol %. The seventh point G represents a composition containing 1 mol % of Li₂O, 94 mol % of SiO₂ and 5 mol % of MO. The eighth point H represents a composition containing 1 mol % of Li₂O, 79 mol % of SiO₂ and 20 mol % of MO. The ninth point I represents a composition containing 19 mol % of Li₂O, 1 mol % of SiO₂ and 80 mol % of MO. The tenth point J represents a composition containing 89 mol % of Li₂O, 1 mol % of SiO₂ and 10 mol % of MO. The eleventh point K represents a composition containing 90 mol % of Li₂O₃, 9 mol % of SiO₂ and 1 mol % of MO and the twelfth point L represents a composition containing 5 mol % of Li₂O, 94 mol % of SiO₂ and 1 mol % of MO. If a Li₂O—SiO₂-Mo composition falls within the range defined by the 6 G-L, as in samples 144, 145, 147 to 149, 151, 152 and 154, the desired electrical characteristics can be obtained, but if otherwise as in samples 143, 146, 150 and 153, a highly densified ceramic body with a highly improved density may not be attained after being sintered at 1300° C.

Further, when the content of Li₂O—SiO₂-MO is 0 wt % as in the sample 138, a highly densified ceramic body may not be obtained by the sintering process at 1300° C.; whereas when the content of Li₂O—SiO₂-MO is set as 0.05 wt % as in sample 139, the desired electrical characteristics can be acquired.

Still further, when the content of Li₂O—SiO₂-MO is 10.00 wt % as in the sample 142, a highly densified ceramic body may not be gained by the sintering at 1300° C.; whereas when the content of Li₂O—SiO₂-MO is set to be 5.00 wt % as in sample 141, the desired electrical characteristics can be successfully obtained.

Accordingly, the content of Li₂O—SiO₂-MO optimally ranges from 0.05 to 5.0 wt %.

Further, when the total content of oxides of Fe, Ni and Cu and oxides of Mn, V and Cr is 0.03 mol % in terms of FeO, NiO, CuO, Mn₂O₃, V₂O₅ and Cr₂O₃ as in the samples 84 to 86, the desired accelerated life may not be obtained; whereas when the total content thereof is 0.04 mol % as in samples 87 to 89, the desired electrical characteristics can be successfully obtained.

Further, when the total content of oxides of Fe, Ni and Cu and oxides of Mn, V and Cr is 1.3 mol % in terms of FeO, NiO, CuO, Mn₂O₃, V₂O₅ and Cr₂O₃, as in the samples 108 to 110, the relative permittivity of produced multilayer ceramic capacitors may go below 3000 or the desired accelerated life may not be attained; whereas when the total content is 1.00 mol % as in samples 105 to 107, the desired electrical characteristics can be successfully obtained.

Accordingly, the total amount of the oxides of Fe, Ni and Cu and the oxides of Mn, V and Cr preferably range from 0.04 to 1.00 mol %.

It should be noted that other types of raw materials can be employed as source materials for obtaining the ceramic slurry. For instance, barium acetate or barium nitrate can be used instead of BaCO₃.

Although the present invention has been described with reference to the multilayer ceramic capacitors only, it should be apparent to those skilled in the art that the present invention can also be applied to single-layer ceramic capacitors.

The present invention can produce a multilayer ceramic capacitor capable of providing a desired accelerated life with a highly improved reliability, wherein the capacitor exhibits a relative permittivity ε_(s) of 3000 or greater, tanδ of 3.5% or less and a capacitance variation ΔC/C₂₅ ranging from −15% to +15% with the temperature variances from −55° C. to +125° C.

While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims. 

What is claimed is:
 1. A dielectric ceramic composition comprising: 100 mol % of an oxide of Ba and Ti; 0.25 to 1.5 mol % of an oxide of Re, Re representing one or more elements selected from the group consisting of Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Y; 0.2 to 1.5 mol % of an oxide of Mg; 0.03 to 0.6 mol % of oxides of one or more elements selected from the group consisting of Mn, V and Cr; 0.025 to 0.25 mol % of oxides of one or two elements of Mo and W; and a glass component including SiO₂.
 2. The dielectric ceramic composition of claim 1, wherein a content of the oxide of Ba and Ti is calculated by assuming that the oxide of Ba and Ti is BaTiO₃; a content of the oxide of Re is calculated by assuming that the oxide of Re is Re₂O₃; a content of the oxide of Mg is calculated by assuming that the oxide of Mg is MgO; a content of oxides of Mn, V and Cr is calculated by assuming that the oxides of Mn, V and Cr are Mn₂O₃, V₂O₅ and Cr₂O₃, respectively; and a content of oxides of Mo and W is calculated by assuming that the oxides of Mo and W are MoO₃ and WO₃, respectively.
 3. The dielectric ceramic composition of claim 2, further comprising one or more oxides selected from the group consisting of oxides of Fe, Ni and Cu and wherein a total content of oxides of Fe, Ni, Cu, Mn, V and Cr is 0.04 to 1.0 mol %, the total content being calculated by assuming that the oxides of Fe, Ni, Cu, Mn, V and Cr are FeO, NiO, CuO, Mn₂O₃, V₂O₅ and Cr₂O₃, respectively.
 4. The dielectric ceramic composition of claim 1, wherein the glass component is composed of Li₂O—BaO—TiO₂—SiO₂ and the content thereof ranges from 0.05 to 1.0 wt %.
 5. The ceramic composition of claim 1, wherein the glass component is composed of B₂O₃—SiO₂-MO, MO representing one or more oxides selected from the group consisting of BaO, SrO, CaO, MgO and ZnO, and wherein a composition of B₂O₃—SiO₂-MO is within a range surrounded by 6 lines formed by cyclically connecting 6 points A, B, C, D, E and F in that order in a triangular composition diagram exhibiting compositional amounts of B₂O₃, SiO₂ and Mo in a unit of mol %, and wherein a point A represents a composition including 1 mol % of B₂O₃, 80 mol % of SiO₂ and 19 mol % of MO, a point B represents a composition including 1 mol % of B₂O₃, 39 mol % of SiO₂ and 60 mol % of MO, a point C represents a composition including 29 mol % of B₂O₃, 1 mol % of SiO₂ and 70 mol % of MO, a point D represents a composition including 90 mol % of B₂O₃, 1 mol % of SiO₂ and 9 mol % of MO, a point E represents a composition including 90 mol % of B₂O₃, 9 mol % of SiO₂ and 1 mol % of MO and a point F represents a composition including 19 mol % of B₂O₃, 80 mol % of SiO₂ and 1 mol % of MO, a content of the composition B₂O₃—SiO₂-MO ranging from 0.05 to 5.0 wt %.
 6. The ceramic composition of claim 1, wherein the glass component is substantially composed of SiO₂ and a content thereof is 0.20 to 4.0 mol %.
 7. The dielectric ceramic composition of claim 1, wherein the glass component is composed of Li₂O—SiO₂-MO, MO representing one or more oxides selected from the group consisting of BaO, SrO, CaO, MgO and ZnO, and wherein the composition of Li₂O—SiO₂-MO is within a range surrounded by 6 lines formed by cyclically connecting 6 points G, H, I, J, K and L in that order in a triangular composition diagram showing compositional amounts of Li₂O, SiO₂ and MO in a unit of mol %, and wherein a point G represents a composition including 1 mol % of Li₂O, 94 mol % of SiO₂ and 5 mol % of MO, a point H represents a composition including 1 mol % of Li₂O, 79 mol % of SiO₂ and 20 mol % of MO, a point I represents a composition including 19 mol % of Li₂O, 1 mol % of SiO₂ and 80 mol % of MO, a point J represents a composition including 89 mol % of Li₂O, 1 mol % of SiO₂ and 10 mol % of MO, a point K represents a composition including 90 mol % of Li₂O₃, 9 mol % of SiO₂ and 1 mol % of MO and a point L represents a composition including 5 mol % of Li₂O, 94 mol % of SiO₂ and 1 mol % of MO, a content of the composition Li₂O—SiO₂-MO ranging from 0.05 to 5.0 wt %.
 8. A ceramic capacitor comprising one or more dielectric layers made of the dielectric ceramic composition of claim
 1. 9. The ceramic capacitor of claim 8, wherein the content of the oxide of Ba and Ti is calculated by assuming that the oxide of Ba and Ti is BaTiO₃; a content of the oxide of Re is calculated by assuming that the oxide of Re is Re₂O₃; a content of the oxide of Mg is calculated by assuming that the oxide of Mg is MgO; a content of oxides of Mn, V and Cr is calculated by assuming that the oxides of Mn, V and Cr are Mn₂O₃, V₂O₅ and Cr₂O₃, respectively; and a content of oxides of Mo and W is calculated by assuming that the oxides of Mo and W are MoO₃ and WO₃, respectively.
 10. The ceramic capacitor of claim 8, wherein the dielectric ceramic composition further comprises one or more oxides selected from the group consisting of oxides of Fe, Ni and Cu and wherein a total content of oxides of Fe, Ni, Cu, Mn, V and Cr is 0.04 to 1.0 mol %, the total content being calculated by assuming that the oxides of Fe, Ni, Cu, Mn, V and Cr are FeO, NiO, CuO, Mn₂O₃, V₂O₅ and Cr₂O₃, respectively.
 11. The ceramic capacitor of claim 8, wherein the glass component is composed of Li₂O—BaO—TiO₂—SiO₂ and the content thereof ranges from 0.05 to 1.0 wt %.
 12. The ceramic capacitor of claim 8, wherein the glass component is composed of B₂O₃—SiO₂-MO, MO representing one or more oxides selected from the group consisting of BaO, SrO, CaO, MgO and ZnO, and wherein a composition of B₂O₃—SiO₂-MO is within a range surrounded by 6 lines formed by cyclically connecting 6 points A, B, C, D, E and F in that order in a triangular composition diagram exhibiting compositional amounts of B₂O₃, SiO₂ and Mo in a unit of mol %, and wherein a point A represents a composition including 1 mol % of B₂O₃, 80 mol % of SiO₂ and 19 mol % of MO, a point B represents a composition including 1 mol % of B₂O₃, 39 mol % of SiO₂ and 60 mol % of MO, a point C represents a composition including 29 mol % of B₂O₃, 1 mol % of SiO₂ and 70 mol % of MO, a point D represents a composition including 90 mol % of B₂O₃, 1 mol % of SiO₂ and 9 mol % of MO, a point E represents a composition including 90 mol % of B₂O₃, 9 mol % of SiO₂ and 1 mol % of MO and a point F represents a composition including 19 mol % of B₂O₃, 80 mol % of SiO₂ and 1 mol % of MO, a content of the composition B₂O₃—SiO₂-MO ranging from 0.05 to 5.0 wt %.
 13. The ceramic capacitor of claim 8, wherein the glass component is substantially composed of SiO₂ and a content thereof is 0.20 to 4.0 mol %.
 14. The ceramic capacitor of claim 8, wherein the glass component is composed of Li₂O—SiO₂-MO, MO representing one or more oxides selected from the group consisting of BaO, SrO, CaO, MgO and ZnO, and wherein the composition of Li₂O—SiO₂-MO is within a range surrounded by 6 lines formed by cyclically connecting 6 points G, H, I, J, K and L in that order in a triangular composition diagram showing compositional amounts of Li₂O, SiO₂ and MO in a unit of mol %, and wherein a point G represents a composition including 1 mol % of Li₂O, 94 mol % of SiO₂ and 5 mol % of MO, a point H represents a composition including 1 mol % of Li₂O, 79 mol % of SiO₂ and 20 mol % of MO, a point I represents a composition including 19 mol % of Li₂O, 1 mol % of SiO₂ and 80 mol % of MO, a point J represents a composition including 89 mol % of Li₂O, 1 mol % of SiO₂ and 10 mol % of MO, a point K represents a composition including 90 mol % of Li₂O₃, 9 mol % of SiO₂ and 1 mol % of MO and a point L represents a composition including 5 mol % of Li₂O, 94 mol % of SiO₂ and 1 mol % of MO, a content of the composition Li₂O—SiO₂-MO ranging from 0.05 to 5.0 wt %. 